Batteries are commonly used electrical energy sources. A battery contains a negative electrode, typically called the anode, and a positive electrode, typically called the cathode. The anode contains an active material that can be oxidized; the cathode contains or consumes an active material that can be reduced. The anode active material is capable of reducing the cathode active material.
When a battery is used as an electrical energy source in a device, electrical contact is made to the anode and the cathode, allowing electrons to flow through the device and permitting the respective oxidation and reduction reactions to occur to provide electrical power. An electrolyte in contact with the anode and the cathode contains ions that flow through the separator between the electrodes to maintain charge balance throughout the battery during discharge.
In certain embodiments, the battery includes a metal as a construction material. For example, the metal can be used to construct a battery container (or can) or a current collector for the positive electrode. Sometimes, the metal can corrode because the electrode potential of the metal is lower than the normal operating potential of the positive electrode of the battery. When the metal is coupled with different metals in the environment of an electrochemical cell, the metal can also be susceptible to corrosion. Corrosion can increase the internal impedance of a cell, leading to capacity loss and to a decrease in specific energy. Corrosion can also limit the choice of metals available as a construction material.